The present invention relates to a catalytic converter for purifying exhaust gases of internal combustion engines.
There are three kinds of catalytic converters, namely a reducing catalytic converter for elimination of nitrogen oxides, an oxidizing catalytic converter for elimination of carbon monoxide and hydrocarbons, and three-way converters for reacting the three noxious elements at the same time. The converters comprise a catalyst bed a pellet type catalyst element or monolithic or honeycomb catalyst element. The monolithic catalyst element is provided in a cylindrical shell, providing resilient supporting means between the cylindrical shell and the element.
The resilient supporting means comprises a wire mesh enclosing the catalyst element and a pair of damper meshes made of wire disposed at opposite ends of the catalyst element, whereby the catalyst element is resiliently supported in the cylindrical shell. Further, the damper mesh at the upstream side of the catalyst element serves as a gas sealing device for preventing the exhaust gases from passing through the gap between the element and the inner wall of the cylindrical shell without contacting the catalyst.
On the other hand, it is difficult to manufacture with precision a cylindrical shell, especially such a cylindrical shell having an oval cross-section and comprising a pair of half shells. Accordingly, the cylindrical shell is liable to have a comparatively large dimensional error. If the gap between the shell and the catalyst element is larger than the tolerance of the converter, sealing the effect of the upstream side damper mesh will decrease.
Further, since the upstream side damper mesh is subjected to the high temperature gases including corrosion components, it has a short lifetime, resulting in early damage to the catalytic converter.
Therefore, it is the object of the present invention to provide a monolithic type catalytic converter having means for compensating the dimensional error of the cylindrical shell and the catalyst element, and thereby providing a converter having a sufficient sealing effect for a long term.